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'-.J; ��"-v��;� TERRA► ASSOCIATES, Inc. <br />'^ '�� Consultants in Geotzchnical Engineering, Geology <br />. <br />�./, _a •_' I <br />_�'< < and <br />Environmental Earth Sciences <br />April 16,1991 <br />Project No. T-1736 <br />Mr. Paul Middleton <br />Middleton Painting <br />5609 Fleming Street <br />Everett, Washington 98203 <br />Subject: Storm Water Infiltration Tests <br />Middleton Painting <br />5609 Fleming Street <br />Everett, Washington <br />Dear Mr. Middleton: <br />Following your request, we performed two storm water infiltration tests at the site of the Middleton Painting <br />building in Everett, Washington. 1Ve understand that storm water [rom portions of your facility will be <br />disposed in an infltration trench. <br />The exact infiltration trench depth is not l:nown at this time and may be dependent on the obsecved <br />subsurface soil horizons. However, we understand that the base of the proposed storm water infiltration <br />trench will be about three to four feet below the existing grade. Two test holes were excavated to a depth of <br />3.5 to 4 feet and presoaked for a few hours. <br />Following the soaking period, water was placed in the test holes and the water level drop was recorded. The <br />approbmate test locations, field infiltration rate and the soil logs ior each of Ihe holes are shown on the <br />attached Table A. The test results indicated that the infiltration rates vary between 13 and 20 minutes per <br />inch. We recommend using a design value of 20 minutes per inch. <br />In addition to the infiltration test holes, a single soil log hole was dug with a rubber tire backhoe near the mid- <br />point of the parking lot approximately Eve feet north of the property line. The log of the test hole is attached <br />as Table B. <br />We hope that this letter has provided you with the requested information for your design needs. Following <br />our field measuremenls, we verbally transmitted the infiltration rates to Group Four, Inc. as soon as they were <br />available. If you havc any questions regarding our tests, please call. <br />Sincerely yours, <br />�RA ASSOCIATCS, IN�. <br />Anil Butail, P.E. <br />President <br />HA/AB:tc <br />cc: Mr. Ray Miller, Group Four, Inc. <br />12525 Willows Road, �uite 101, Kirkland, Washington 98034 • Phone (206) 821-7777 • rax n�i-aa�� <br />